Date of Award:

5-2014

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Chemistry and Biochemistry

Committee Chair(s)

Lance C. Seefeldt

Committee

Lance C. Seefeldt

Committee

Scott A. Ensign

Committee

Alvan C. Hengge

Committee

Sean J. Johnson

Committee

Korry Hintze

Abstract

The reduction of nitrogen to ammonia by the industrial Haber-Bosch process is considered one of the major scientific breakthroughs of the last century. It is considered to be responsible for approximately one third of the world's current population. This growth over the past 50 or so years accompanied by the changes in dietary habits due to economic growth have markedly increased the demand for fixed nitrogen in the form of fertilizer. The Haber-Bosch process and biological nitrogen fixation has been able to fulfil this demand. However, this industrial process is costly due to its high temperature and pressure requirements. Every year, approximately 2% of the total global energy is used to manufacture fixed nitrogen (ammonia). Microorganisms like the diazotrophs though, can fix nitrogen at a fraction of the cost. Research in the field of biological nitrogen fixation could prove valuable in understanding the mechanism of the enzyme responsible, nitrogenase which could eventually allow researchers to mimic the enzyme and fix nitrogen at room temperature and pressure. In the current climate of energy awareness, this should be a high priority.

Nitrogenase, the enzyme responsible for nitrogen fixation in nature, has two component proteins that associate and dissociate multiple times to reduce nitrogen. This was studied to understand the order of events in association and dissociation such as; electron transfer, ATP hydrolysis, and phosphate release. When the two components associate, the induce movements within the enzyme complex. These movements, called conformational changes, are responsible for the ability of the enzyme to reduce nitrogen at room temperature and pressure. The conformational changes, and their effect on the reduction of substrates was also studied. This knowledge was used to find and study modified forms of one half of nitrogenase that could be activated using controlled external reductants. This freedom from the association and dissociation events opens the door for further research into the understanding and development of enzyme mimics that can reduce sbstrates at room temperature and pressure.

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